Centrifugal compressors include a rotor or impeller having a hub provided with a plurality of vanes. The vanes have discharge ends and when rotated with the hub, act to impel the fluid to be compressed toward the discharge ends of the blades. Generally speaking, there are two definitive types of such compressors. One type may be termed an axial discharge compressor which directs the fluid subject to compression in an axial direction as it leaves the rotor. Another type is a radial discharge compressor which, in operation, discharges the fluid to be compressed in the radial direction.
Further, there are a large variety of compressors that have characteristics of both axial flow and radial flow compressors.
In the case of radial discharge compressors, the discharge ends of the blades are on the order of being parallel with the rotational axis of the rotor. Disposed about the rotor is a radial diffuser which typically is provided with a plurality of spaced diffuser blades which extend from an annular inlet to the diffuser away from the compressor blades toward an outlet. In simplest terms, the purpose of the diffuser is to create an elevated pressure in the fluid being driven by the compressor blades from the high velocity imparted to such fluid by those blades.
Compressors of this sort are susceptible to many uses. One common use is as a compressor stage of a turbine engine. Given fuel concerns of the last decade, considerable effort has been expended in attempting to increase the efficiency of operation of turbine engines and amongst others, one area focused upon has been diffuser geometry. In many instances, the attention has been directed to the configuration of the leading edges of the diffuser blades, that is, the edges of the diffuser blandes that are located most closely to the discharge ends of the impeller baldes. Representative of various approaches taken in this area are U.S. Pat. Nos. 2,967,013 issued Jan. 3, 1961 to Dallenbach et al; 3,832,089 issued Aug. 27, 1974 to Moellmann; 4,349,314 issued Sept. 14, 1982 to Erwin; and 3,904,312 issued Sept. 9, 1975 to Exley.
The present invention is directed to improving on these and other efforts so as to increase the efficiency of a turbine engine with which the diffuser may be utilized, including increasing the compressor surge margin thereof.